The trouble with building mobile computing applications is that end users have little tolerance when it comes to how they expect those applications to behave. Never mind the fact that mobile applications are amongst some of the most challenging to create; the second somebody has a less than optimal experience they're off to another application. Needless to say, that puts a lot of pressure on mobile application developers.
In January, OnStar announced an API would allow third party developers to integrate their applications with OnStar's platform. Last week, General Motors announced its first partner for API integration: RelayRides. RelayRides is "[t]he world's largest peer to peer carsharing marketplace." The partnership with GM allows OnStar users to leave their keys in their cars when renting a car to a fellow RelayRider. The renter can then unlock the car with a smartphone app or by responding to a text message.